This invention relates to an apparatus for removing a bag from an article enclosed by the bag.
Apparatus according to the present invention may be utilized, for example, in the canning industry to remove an elongated paper bag from a long, cylindrical stack of can covers preparatory to use of the can covers in a canning operation. Ordinarily, before any such bag is removed from the stack of can covers enclosed therewith, the bag is slit longitudinally.
Prior to the present invention, apparatus such as that depicted schematically in FIG. 1 has been utilized for removing bags from stacks of can covers. The FIG. 1 apparatus includes a pair of horizontal, parallel arranged shafts 1 and 1' and two cylindrical support rolls 2 and 2' mounted on the shafts. Rolls 2 and 2' are covered with a resilient material and such rolls define a nip 7 therebetween. A pair of positioning rods 3 and 3' are disposed above the support rolls and extend parallel thereto. A bag Z enclosing an enlongated article A may be placed atop support rolls 2 and 2' between positioning rods 3 and 3' so that the bag rests on the support rolls, the long axes of the bag and article extending parallel to the support rolls. Normally, the bag is positioned so that the slit is at the top. A U-shaped pressure member 4 is forced downwardly onto the bag and article so that the lower portions 5 and 5' of the pressure member engage the bag and the article. As the article is forced downwardly by the pressure member, it in turn forces the lower portions of the bag overlying support rolls 2 and 2' into engagement with the support rolls at contact lines 6 and 6'. Support roll 2 is rotated in the clockwise direction as seen in FIG. 1 and support roll 2' is rotated in the counterclockwise direction. Such rotation of the support rolls draws the bag into the nip between the rolls and pulls it away from the article. As the bag is pulled away from the article, it is fed through the nip 7 and discharged from the apparatus onto a belt conveyor (not shown) which transports the bag to a storage container. The article A remains atop the support rolls when the bag is pulled away from it. After the bag is removed from the article, the article can be removed from the apparatus for further processing.
The bag may have thick, folded portions at its ends. Such portions generally are not pulled away from the article during the initial stages of the removal procedure. Rather, the midsection of the bag remote from the thick portions is fed into the nip 7 between the support rolls first. Once the midsection of the bag is firmly engaged between the support rolls in the nip, continued rotation of the support rolls feeds the midsection through the nip and pulls the thick portions at the ends of the bag into the nip. The end portions of the bag generally advance through the nip at different times. If one such end portion is thicker than the other, the thicker end portion will generally be fed through the nip last. Accordingly, the bag does not advance through the nip uniformly. Instead, the misection of the bag generally advances through the nip first, followed by one end of the bag and then the other end.
This nonuniform advancement of the bags through the nip between the support rolls may cause difficulties when the bags fall onto the belt conveyor. The first portion of a bag to pass through the nip may encounter the moving belt of the conveyor before the last portion of the bag has cleared the nip. Accordingly, the bags may be bent or stretched unpredictably as they encounter the conveyor belt, and the bags may be deposited on the conveyor belt in unpredictable orientations. Portions of some of the bags may project beyond the lateral margins of the conveyor belt and become entangled with other portions of the apparatus, causing a jam of bags on the conveyor. Moreover, because the bags are oriented at random on the conveyor belt, the bags will be fed into the storage container at random and stored therein in a random stack. Such random stacking wastes space within the storage container, especially when the bags are rather long (e.g., about 90 cm. long). Therefore, the storage container must be changed at frequent intervals during operation of the apparatus.
In some installations, the belt conveyor must make a right angle bend to accommodate space limitations in the building where the apparatus is used. The long bags can cause difficulties at such a bend in the conveyor.
Also, it is sometimes difficult to attain adequate frictional engagement between the bag and the support rolls at the lines of contact 6 and 6' in the apparatus shown in FIG. 1. The axes 0.sub.1 and 0.sub.2 of the support rolls are close to one another so that the angle .theta. subtended by imaginary planes 00.sub.1 and 00.sub.2 at the center 0 of article A is small. This arrangement of the support rolls limits the forces which will be applied to urge the bag against the support rolls at the lines of contact 6 and 6'. With the arrangement of rollers illustrated in FIG. 1, the sum of such forces generally will not be substantially greater than the downward force applied by pressure member 4. This downward force in turn is limited by structural considerations. If the downward force applied by the pressure member is too great, the support rolls and shafts can be bent and the article in the bag can be damaged. However, if the forces applied to urge the bag against the support rolls at contact lines 6 and 6' are not great enough, the frictional engagement of the bag with the support rolls may be inadequate to pull the bag away from the article.